The present invention relates to a presetting device having an anti-friction bearing bushing for receiving the bearing pin of a tool to be measured, both the pin and the bushing having conical surfaces.
Types of such devices are used in so-called machining centers where a large number of replaceable tools or precision tools are present. They must be measured and preset in the presetting device prior to use, which is effected in the manner that the, generally conical, bearing pins of the tools are placed in the corresponding conical bearing sleeve of the device and measured--and if necessary also adjusted--in several positions by rotation within the bearing bushing.
Due to the weight of the tool itself, which may be considerable in the case of larger tools, rotation in the bearing sleeve is ordinarily scarcely possible or possible only with the application of a high force, since the friction between the surface of the pin and the inner surface of the cone of the bearing sleeve is relatively great. Specifically, however, upon the measuring of precision tools, it is necessary that the tools be easily rotatable within the bearing sleeve.
In accordance with a proposal known from Federal Republic of Germany A-1 951 151, it has been, attempted to remedy this problem by supporting the tool with a bearing sleeve with cylindrical outer wall surface via an anti-friction bearing rolling on said outer wall surface within a cylindrical bearing bushing. The disadvantage of this solution is that the two anti-friction bearings must agree very precisely since, otherwise, they give rise to inaccuracies. Such anti-friction bearings are extremely expensive. Furthermore, there is the danger that the bearing sleeve or the anti-friction bearing have play so that the required trueness of concentricity is no longer assured upon measurement.